Maternal and fetal influences on uterine and conceptus development in the cow: I. Growth of tissues of the gravid uterus.

Objectives of this study were to evaluate maternal and fetal influences on development of gravid uterine tissues of cows. Brahman cows with Brahman or Charolais fetuses and Charolais cows with Brahman or Charolais fetuses were used. Cows were killed 232 +/- .5 or 271 +/- .7 d after mating. The gravid uterus of each cow was weighed and dissected into its component parts. Weights of the fetus, fetal membranes, cotyledons, caruncles, and uterus were recorded as were weights of the fetal liver, heart, kidneys, spleen, lungs, stomach complex, intestines, and semitendinosus muscle. Ribonucleic acid, DNA, and protein concentrations in caruncles, cotyledons, liver, heart, kidney, and semitendinosus muscle were determined. Data were analyzed by analysis of variance; breed of cow (C), breed of fetus (F), day of gestation (D), and all interactions were included in the model as fixed effects. Fetal weights were influenced (P less than .003) by C, F, D, and C x D and tended (P = .07) to be influenced by C X F X D. Weight, RNA, DNA, and protein contents of selected fetal tissues followed similar patterns of significance. Thus, both maternal and fetal genotype influenced fetal growth. Greater influences of the maternal system and interrelationships between maternal and fetal systems were observed at the latter stage of gestation. Placentomal (caruncle + cotyledon) weights were greater for Charolais than for Brahman cows (P less than .02) or fetuses (P less than .001) and were greater (P less than .01) at 271 than at 232 d. Caruncular weights followed similar patterns; however, fetal genotype was the only significant source of variation in cotyledonary weight, RNA, DNA, or protein content.(ABSTRACT TRUNCATED AT 250 WORDS)